Q: How to downgrade iTunes 11 to previous version 10.7

Roll back with Time Machine.

Even with Time Machine it won't let you replace itunes 11 because it says that iTunes is needed by the Operating System.

I have done just this, and I got iTunes giving me an unknown error "42408". So I deleted everything relating to itunes, the frameworks, updated library files, mobiledevice stuff, etc. I then did a clean install of iTunes 10.7, now I still get the same error when I try to authenticate my iTunes account. I and login and sign out of the account in itunes fine, but if I try to authorize or sync my iPad I will get this error and not let me proceed.

I had a copy of the install dmg in a time machine backup. I spent about 30 minutes digging through my downloads folder backups to find it.

http://appldnld.apple.com/iTunes10/041-7195.20120912.d3uzQ/iTunes10.7.dmg

<This is a Direct Download Link>

Even with this you will still not be able to open your iTunes library without a backup of it prior to the update to v11.

Use Time Machine backup if yo uhave one. And you re done.

How do you reinstall using a backup from Time Machine?
I'm trying for the second time, replacing the folders HD/users/me/music and HD/Applications/iTunes.app.  It didn't work the first time (after replacing almost 90GB of data) and I'm sceptical about it working this time.
There are lots of threads appearing with this issue, but no proven solution yet.
If you know another method to reinstall iTunes from TM I'd be grateful to hear it.

if you go to itunes and view your account you can use the button to de-authorize all your computers. That should de-authorize so you can re-authorize.

I've tried that but to no avail - I get the same error message - 42408.

Same problem here. Any info appreciated...